In physics terms the difference between viscous and viscoelasticity

is that viscous is of or pertaining to viscosity while viscoelasticity is the branch of rheology that studies such materials.

As an adjective viscous

is having a thick, sticky consistency between solid and liquid.

As a noun viscoelasticity is

the property of a material that is both viscous and elastic.

As nouns the difference between elastic and viscoelasticity

is that elastic is an elastic material used in clothing, particularly in waistbands and cuffs while viscoelasticity is the property of a material that is both viscous and elastic.

As an adjective elastic

is capable of stretching; particularly, capable of stretching so as to return to an original shape or size when force is released.

In physics|lang=en terms the difference between rheology and viscoelasticity

is that rheology is (physics) the branch of physics that studies the deformation and flow of matter while viscoelasticity is (physics) the branch of rheology that studies such materials.

As nouns the difference between rheology and viscoelasticity

is that rheology is (physics) the branch of physics that studies the deformation and flow of matter while viscoelasticity is (physics) the property of a material that is both viscous and elastic.

Anticipate is a synonym of proact.

As verbs the difference between anticipate and proact

is that anticipate is to act before (someone), especially to prevent an action while proact is to take action in advance of an expected event.

As nouns the difference between official and officialese

is that official is an office holder invested with powers and authorities while officialese is the typical language of officials or official documents; legalistic and pompous language.

As an adjective official

is of or pertaining to an office or public trust.

As an adjective legalistic

is of a person, following the letter of the law.

As a noun officialese is

the typical language of officials or official documents; legalistic and pompous language.

As an adjective pompous

is affectedly grand, solemn or self-important.

As a noun officialese is

the typical language of officials or official documents; legalistic and pompous language.

As nouns the difference between legalese and officialese

is that legalese is the technical talk of the legal profession, the argot of lawyers while officialese is the typical language of officials or official documents; legalistic and pompous language.

As nouns the difference between book and sourcebook

is that book is book while sourcebook is a book consisting of a collection of writings on a particular subject.

As nouns the difference between publication and sourcebook

is that publication is the act of publishing printed or other matter while sourcebook is a book consisting of a collection of writings on a particular subject.